/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.yixia.zi.utils;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.TransitionDrawable;
import android.widget.ImageView;

import com.yixia.zi.BuildConfig;

import java.lang.ref.WeakReference;
import java.util.Hashtable;
import java.util.concurrent.RejectedExecutionException;

/**
 * This class wraps up completing some arbitrary long running work when loading
 * a bitmap to an ImageView. It handles things like using a memory and disk
 * cache, running the work in a background thread and setting a placeholder
 * image.
 */
public abstract class ImageWorker {
	private static final String TAG = "ImageWorker";
	private static final int FADE_IN_TIME = 200;

	protected ImageCache mImageCache;
	protected Bitmap mLoadingBitmap;
	protected boolean mFadeInBitmap = true;
	private boolean mExitTasksEarly = false;
	private final Hashtable<Integer, Bitmap> loadingBitmaps = new Hashtable<Integer, Bitmap>(2);

	protected Context mContext;

	protected ImageWorker(Context context) {
		mContext = context;
	}

	/**
	 * Load an image specified by the data parameter into an ImageView (override
	 * {@link ImageWorker#processBitmap(Object)} to define the processing logic).
	 * A memory and disk cache will be used if an {@link ImageCache} has been set
	 * using {@link ImageWorker#setImageCache(ImageCache)}. If the image is found
	 * in the memory cache, it is set immediately, otherwise an {@link AsyncTask}
	 * will be created to asynchronously load the bitmap.
	 * 
	 * @param data The URL of the image to download.
	 * @param imageView The ImageView to bind the downloaded image to.
	 */
	protected void loadImage(Object data, ImageView imageView) {
		loadImage(data, imageView, mLoadingBitmap);
	}

	/**
	 * Load an image specified by the data parameter into an ImageView (override
	 * {@link ImageWorker#processBitmap(Object)} to define the processing logic).
	 * A memory and disk cache will be used if an {@link ImageCache} has been set
	 * using {@link ImageWorker#setImageCache(ImageCache)}. If the image is found
	 * in the memory cache, it is set immediately, otherwise an {@link AsyncTask}
	 * will be created to asynchronously load the bitmap.
	 * 
	 * @param data The URL of the image to download.
	 * @param imageView The ImageView to bind the downloaded image to.
	 * @param resId Resource of placeholder bitmap while the image loads.
	 */
	protected void loadImage(Object data, ImageView imageView, int resId) {
		if (!loadingBitmaps.containsKey(resId)) {
			// Store loading bitmap in a hash table to prevent continual decoding
			loadingBitmaps.put(resId, BitmapFactory.decodeResource(mContext.getResources(), resId));
		}
		loadImage(data, imageView, loadingBitmaps.get(resId));
	}

	/**
	 * Load an image specified by the data parameter into an ImageView (override
	 * {@link ImageWorker#processBitmap(Object)} to define the processing logic).
	 * A memory and disk cache will be used if an {@link ImageCache} has been set
	 * using {@link ImageWorker#setImageCache(ImageCache)}. If the image is found
	 * in the memory cache, it is set immediately, otherwise an {@link AsyncTask}
	 * will be created to asynchronously load the bitmap.
	 * 
	 * @param data The URL of the image to download.
	 * @param imageView The ImageView to bind the downloaded image to.
	 * @param loadingBitmap The placeholder bitmap while the image loads.
	 */
	protected void loadImage(Object data, ImageView imageView, Bitmap loadingBitmap) {
		Bitmap bitmap = null;

		if (mImageCache != null) {
			bitmap = mImageCache.getBitmapFromMemCache(String.valueOf(data));
		}

		if (bitmap != null) {
			// Bitmap found in memory cache
			imageView.setImageBitmap(bitmap);
		} else if (cancelPotentialWork(data, imageView)) {
			final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
			final AsyncDrawable asyncDrawable = new AsyncDrawable(mContext.getResources(), loadingBitmap, task);
			imageView.setImageDrawable(asyncDrawable);
			executeTaskInParallel(data, task);
		}
	}

	/**
	 * Executes the given {@link BitmapWorkerTask} in parallel. On Honeycomb the
	 * default executor is a serial executor so we explicitly use a parallel
	 * (thread pool) executor.
	 */
	private void executeTaskInParallel(Object data, BitmapWorkerTask task) {
		try {
			task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, data);
		} catch (RejectedExecutionException e) {
			Log.e("localRejectedExecutionException", e);
		}
	}

	/**
	 * Set placeholder bitmap that shows when the the background thread is
	 * running.
	 */
	public void setLoadingImage(Bitmap bitmap) {
		mLoadingBitmap = bitmap;
	}

	/**
	 * Set placeholder bitmap that shows when the the background thread is
	 * running.
	 */
	public void setLoadingImage(int resId) {
		mLoadingBitmap = BitmapFactory.decodeResource(mContext.getResources(), resId);
	}

	/**
	 * Set the {@link ImageCache} object to use with this ImageWorker.
	 */
	public void setImageCache(ImageCache cacheCallback) {
		mImageCache = cacheCallback;
	}

	public ImageCache getImageCache() {
		return mImageCache;
	}

	/**
	 * If set to true, the image will fade-in once it has been loaded by the
	 * background thread.
	 */
	public void setImageFadeIn(boolean fadeIn) {
		mFadeInBitmap = fadeIn;
	}

	public void setExitTasksEarly(boolean exitTasksEarly) {
		mExitTasksEarly = exitTasksEarly;
	}

	/**
	 * Subclasses should override this to define any processing or work that must
	 * happen to produce the final bitmap. This will be executed in a background
	 * thread and be long running. For example, you could resize a large bitmap
	 * here, or pull down an image from the network.
	 * 
	 * @param data The data to identify which image to process, as provided by
	 * {@link ImageWorker#loadImage(Object, ImageView)}
	 * @return The processed bitmap
	 */
	protected abstract Bitmap processBitmap(Object data);

	public static void cancelWork(ImageView imageView) {
		final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
		if (bitmapWorkerTask != null) {
			bitmapWorkerTask.cancel(true);
			if (BuildConfig.DEBUG) {
				final Object bitmapData = bitmapWorkerTask.data;
				Log.d(TAG, "cancelWork - cancelled work for " + bitmapData);
			}
		}
	}

	/**
	 * Returns true if the current work has been canceled or if there was no work
	 * in progress on this image view. Returns false if the work in progress deals
	 * with the same data. The work is not stopped in that case.
	 */
	public static boolean cancelPotentialWork(Object data, ImageView imageView) {
		final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);

		if (bitmapWorkerTask != null) {
			final Object bitmapData = bitmapWorkerTask.data;
			if (bitmapData == null || !bitmapData.equals(data)) {
				bitmapWorkerTask.cancel(true);
				if (BuildConfig.DEBUG) {
					Log.d(TAG, "cancelPotentialWork - cancelled work for " + data);
				}
			} else {
				// The same work is already in progress.
				return false;
			}
		}
		return true;
	}

	/**
	 * @param imageView Any imageView
	 * @return Retrieve the currently active work task (if any) associated with
	 * this imageView. null if there is no such task.
	 */
	private static BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {
		if (imageView != null) {
			final Drawable drawable = imageView.getDrawable();
			if (drawable instanceof AsyncDrawable) {
				final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;
				return asyncDrawable.getBitmapWorkerTask();
			}
		}
		return null;
	}

	/**
	 * The actual AsyncTask that will asynchronously process the image.
	 */
	private class BitmapWorkerTask extends AsyncTask<Object, Void, Bitmap> {
		private Object data;
		private final WeakReference<ImageView> imageViewReference;

		public BitmapWorkerTask(ImageView imageView) {
			imageViewReference = new WeakReference<ImageView>(imageView);
		}

		/**
		 * Background processing.
		 */
		@Override
		protected Bitmap doInBackground(Object... params) {
			data = params[0];
			final String dataString = String.valueOf(data);
			Bitmap bitmap = null;

			// If the image cache is available and this task has not been
			// cancelled by another
			// thread and the ImageView that was originally bound to this task
			// is still bound back
			// to this task and our "exit early" flag is not set then try and
			// fetch the bitmap from
			// the cache
			if (mImageCache != null && !isCancelled() && getAttachedImageView() != null && !mExitTasksEarly) {
				bitmap = mImageCache.getBitmapFromDiskCache(dataString);
			}

			// If the bitmap was not found in the cache and this task has not
			// been cancelled by
			// another thread and the ImageView that was originally bound to
			// this task is still
			// bound back to this task and our "exit early" flag is not set,
			// then call the main
			// process method (as implemented by a subclass)
			if (bitmap == null && !isCancelled() && getAttachedImageView() != null && !mExitTasksEarly) {
				bitmap = processBitmap(params[0]);
			}

			// If the bitmap was processed and the image cache is available,
			// then add the processed
			// bitmap to the cache for future use. Note we don't check if the
			// task was cancelled
			// here, if it was, and the thread is still running, we may as well
			// add the processed
			// bitmap to our cache as it might be used again in the future
			if (bitmap != null && mImageCache != null) {
				mImageCache.addBitmapToCache(dataString, bitmap);
			}

			return bitmap;
		}

		/**
		 * Once the image is processed, associates it to the imageView
		 */
		@Override
		protected void onPostExecute(Bitmap bitmap) {
			// if cancel was called on this task or the "exit early" flag is set
			// then we're done
			if (isCancelled() || mExitTasksEarly) {
				bitmap = null;
			}

			final ImageView imageView = getAttachedImageView();
			if (bitmap != null && imageView != null) {
				setImageBitmap(imageView, bitmap);
			}
		}

		/**
		 * Returns the ImageView associated with this task as long as the
		 * ImageView's task still points to this task as well. Returns null
		 * otherwise.
		 */
		private ImageView getAttachedImageView() {
			final ImageView imageView = imageViewReference.get();
			final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);

			if (this == bitmapWorkerTask) {
				return imageView;
			}

			return null;
		}
	}

	/**
	 * A custom Drawable that will be attached to the imageView while the work is
	 * in progress. Contains a reference to the actual worker task, so that it can
	 * be stopped if a new binding is required, and makes sure that only the last
	 * started worker process can bind its result, independently of the finish
	 * order.
	 */
	private static class AsyncDrawable extends BitmapDrawable {
		private final WeakReference<BitmapWorkerTask> bitmapWorkerTaskReference;

		public AsyncDrawable(Resources res, Bitmap bitmap, BitmapWorkerTask bitmapWorkerTask) {
			super(res, bitmap);

			bitmapWorkerTaskReference = new WeakReference<BitmapWorkerTask>(bitmapWorkerTask);
		}

		public BitmapWorkerTask getBitmapWorkerTask() {
			return bitmapWorkerTaskReference.get();
		}
	}

	/**
	 * Called when the processing is complete and the final bitmap should be set
	 * on the ImageView.
	 */
	@SuppressWarnings("deprecation")
	private void setImageBitmap(ImageView imageView, Bitmap bitmap) {
		if (mFadeInBitmap) {
			// Use TransitionDrawable to fade in.
			final TransitionDrawable td = new TransitionDrawable(new Drawable[] { new ColorDrawable(android.R.color.transparent), new BitmapDrawable(mContext.getResources(), bitmap) });
			//noinspection deprecation
			imageView.setBackgroundDrawable(imageView.getDrawable());
			imageView.setImageDrawable(td);
			td.startTransition(FADE_IN_TIME);
		} else {
			imageView.setImageBitmap(bitmap);
		}
	}

	public void setPauseDiskCache(boolean pause) {
		if (mImageCache != null) {
			mImageCache.setPauseDiskCache(pause);
		}
	}

	public void closeCache() {
		if (mImageCache != null) {
			mImageCache.close();
		}
	}
}
